If [Harry Potter and the Cursed Child] continues to sell at this rate, it will be the second biggest-selling single week for one title since records began, with Harry Potter and the Deathly Hallows as the first, which sold 1.8m copies plus 780,000 units of the adult edition in its launch week in July 2007.

The success of the Harry Potter and the Cursed Child script has prompted the Palace Theatre London to extend production of the Harry Potter play through December 2017. An new batch of 250,000 tickets will go on sale Thursday, with prices starting at just £15 per part.